1. Field of the Invention
This invention relates generally to a brightness control system and, more particularly, to an adaptive instrument display brightness control system that automatically controls the illumination of a vehicle instrument display based on a vehicle operator's adjustment of the illumination intensity of the display and the ambient light condition.
2. Discussion of the Related Art
Current technology in the manufacture of vehicles includes advancements directed to personalization of certain vehicle systems to a particular vehicle operator. One particular personalization advancement is in an electronic climate control system as disclosed in U.S. patent application Ser. No. 08/344,189, filed Nov. 23, 1994, titled ADAPTIVE CLIMATE CONTROL SYSTEM, assigned to the assignee of the instant application, and herein incorporated by reference. This adaptive climate control system is an improvement on known electronic climate control (ECC) systems that automatically control the climate within the passenger compartment of a vehicle based on a number of parameters that affect the climate. These parameters are initially preprogrammed and calibrated to a particular comfort level by a climate control calibration engineer at the manufacturing level of the vehicle.
The adaptive ECC system allows adjustments to the control of the system by a particular vehicle operator to teach the system to automatically be set to the operator's comfort level. For example, if the vehicle operator adjusts the temperature set point of the ECC system at a particular ambient air temperature, the system will store this change for that ambient air temperature. Once the change has been validated, the next time the system encounters that ambient air temperature, or an ambient air temperature around that ambient air temperature, the system will automatically provide the appropriate air mixture as previously set by the vehicle operator. Further, the adaptive ECC system will adapt the blower speed to the preference of the vehicle operator. Each time the vehicle operator adjusts the blower speed to a particular value for a set of environmental conditions, and the adaptive system validates the change in blower speed, the system will automatically readjust the blower speed for subsequent similar environmental conditions sensed by the system.
The concept of adapting certain vehicle systems to a particular vehicle operator's preferences can be extended to other vehicle systems in addition to the vehicle climate control system. For example, another adaptive vehicle control system automatically adjusts the volume gain of a vehicle audio system in response to ambient noise such as changes in engine speed, climate control mode and blower speed in connection with a vehicle operator's adjustment of the audio system volume level as disclosed in U.S. patent application Ser. No. 08/437,555, filed May 9, 1995, titled ADAPTIVE SYSTEM FOR DETERMINING VOLUME GAIN FOR VEHICLE AUDIO SYSTEMS. Another adaptive system sets the radio frequency of a vehicle radio at vehicle start-up depending on the vehicle operator's preference at a particular time of day as disclosed in U.S. patent application Ser. No. 08/441,109, filed May 15, 1995, titled ADAPTIVE SYSTEM FOR DETERMINING RADIO FREQUENCY AT VEHICLE START-UP. Both of these applications are assigned to and are herein incorporated by reference. Still, other vehicle systems can benefit from these types of adaptive control systems.
Another system that can benefit from being adapted to a vehicle operator's preference is the brightness of the instrument display of the vehicle. All, or most all, vehicles incorporate some type of instrument display lighting so that the vehicle operator can easily view the vehicle's instruments in all ambient light conditions. Different types of instrument display illumination includes instrument backlighting, analog pointer lights, liquid crystal displays (LCDs) and vacuum florescent (VF) tubes. VF tubes are also used to provide the illumination intensity for head-up displays (HUDs) as is well known to one skilled in the art. Generally, the vehicle will include an illumination intensity switch that allows the vehicle operator to adjust the intensity of the instrument display or HUD as the operator desires.
Instrument display lighting creates heat relative to the intensity of the light. Continuous high intensity illumination of an instrument display will therefore reduce the reliability of the instruments because continued and excessive heat may affect their performance. In order to at least reduce the need to continually adjust the instrument display illumination and to limit the intensity of the instrument display illumination, it is advantageous to incorporate an adaptive illumination control system that automatically sets the instrument display illumination and is responsive to changes that a vehicle operator makes to the instrument display brightness control with respect to the ambient light conditions. Therefore, it is an object of the present invention to provide such an adaptive system.